PROJECT SUMMARY/ABSTRACT Youth are using electronic cigarettes (e-cigarettes) at a rapidly increasing rate [1, 2]. Unfortunately, there is a lack of scientific knowledge regarding why e-cigarettes are appealing to youth, the effects of e- cigarette use, and how e-cigarette marketing is influencing adolescents' beliefs, intentions, and willingness to use these novel tobacco products. Since e-cigarettes are unregulated, a generation of adolescents who have never seen cigarettes being widely promoted are currently being exposed to e-cigarette marketing across a wide variety of mediums. As the Food and Drug Administration (FDA) moves to regulate e-cigarettes, critical gaps in the research literature regarding the impact of e-cigarette marketing, access to products, and initiation and use are hindering policy makers. Study aims are to: (1) Examine prevalence of lifetime use and patterns of current use of e-cigarettes among middle school students (ages 11-14) across a school year; (2) Assess concurrent and prospective factors related to initiation and use of e-cigarettes among middle school students, including perceptions of risk, social images of users, motives for using, intentions and willingness to use, access to products, and exposure to marketing; and (3) Explore associations between e-cigarette initiation and co-use or willingness and intentions to use other tobacco products as well as symptoms of dependence on nicotine as a result of using e-cigarettes. Additional factors shown to be related to adolescent tobacco use, such as race/ethnicity and level of acculturation, will also be considered in order to provide a comparison between e-cigarettes and traditional tobacco products. To accomplish our aims, we will conduct two longitudinal school-based surveys across a school year (Fall and Spring) in two middle schools (N = 1,150; half Hispanic). Based on information obtained in the school surveys, we will select a subsample of e-cigarette users (N = 60) for in-depth interviews, to gather additional information on the contexts surrounding e-cigarette use, to obtain sequential details of co-use with other tobacco products, and to delve more deeply into the appeal and motivations to use e-cigarettes in this population. This project will directly contribute to the currently sparse body of research on e-cigarettes and youth, guide future e-cigarette regulation by the FDA, and provide information that can assist in the development of counter-marketing strategies targeting youth as well as strategies to limit minors' access to e-cigarettes. It will also contribute to models of adolescent risk taking and novel tobacco use.